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Ultrafast Dynamics of Tamm Plasmon-Polaritons in Metal/Photonic Crystal System
B.I. Afinogenov, V.O. Bessonov and A.A. Fedyanin
Lom onosov M oscow St at e Uni versit y, 1 Leni nski e gory, 119991, M oscow, Russi a afi nogenov@nanolab.phys.m su.ru

Abstra ct: Measurements of temp oral p rofiles of femtosecond pulses reflected fr om metal/p hotonic cr ystal s ystem show that the pulses are distorted when spectra of the pump laser radiation and r esonance line of Tamm p lasmon-polariton overlap. Lifetime of TPP was estimated at 30 fs.
OCIS codes: ( 350.4238) Nanophotonics and phot oni c cr yst als; (320.2250) Femtosecond phenome na

1 . Introduction Tamm p lasmon-polar itons (TPP) in photonic crystals (PC) are op tical analogues of electronic densit y localization at the boundar y of p eriodic atomic potential [1] and ap pear as electromagnetic field localization at the boundar y of p hotonic cr ystal and metal [2]. Unlike sur face electromagnetic waves and sur face plasmon-p olaritons (SPP) Tamm p lasmon-p olaritons do not have p hase-matching conditions for in-plane wave vector, thus TPP can b e excited for any angle of incidence [3]. However b oundar y conditions for out-of-p lane wave vector are critical for TPP. Experimentall y these states manifest themselves as narr ow absorption gaps in reflectance spectra of Me/PC systems[4 ]. U ltrafast d ynamics of SPP was intensively studied last years. Significant distor tion of femtosecond p ulses travelling in plasmonic nanostructures was shown [5 -7 ]. Ultrafast measurements can p rovide infor mation about lifetime and excitation dynamics of the TPP which is of the great fundamental interest and on the other hand is useful for the creating b rand new devices for contr olling the light. However to the b est of our know ledge there are no papers in which ultr afast dynamics of Tamm p lasmon-polaritons is studied. 2 . Samples and setup The studied samp les consisted of 6 p airs of ZrO2/SiO2 (average thicknesses 110 nm and 145 nm respectivel y) q uarter-wavelength layers with SiO2 la yer on top, deposited on quartz substrate using thermal evap oration. Accor ding to the calculations optimal thickness of the top most layer was estimated as 225 nm, therefore additional 80 nm la yer of SiO 2 was dep osited on a sample using thermal evap or ation. The resultant structure was covered b y a 30-nm-thick gold film allowing good field localization in the TPP. 30-nm-thick gold film on quartz sub strate was used as a reference sample. As a source Ti:Sapp hire laser with p ulse precompressor was used, p roviding 30 fs p ulses w ith 8 0 MHz rep etition rate. Polarization of incident light was contr olled with a wideb and half-wavelength p late. Temporal p rofiles of femtosecond p ulses, reflected from the Au/PC sample, were ob tained using noncollinear intensit y crosscorrelation measur ements. 3 . Experimenta l results Experimental cr oss-corr elation function of p ulse reflected fr om 3 0-nm-thick gold film is shown in Fig. 1a with dots in a semilogarithmic scale. Corresp onding sp ectrum of a pulse is shown in the inset. Profile of a p ulse is in an excellent agreement with Gaussian fit, show n with red solid curve. Cross-correlation functions of p- and s-p olarized p ulses reflected fr om the Au/PC samp le are shown in Fig. 1b with black squares and r ed circles respectivel y. Inset shows corr esponding spectra of p- (b lack cur ve) and s- (red cur ve) p olarized incoming light reflected fr om the Au/PC samp le. Dips, related to the TPP exist in b oth p olarizations, but overlapp ing of TPP resonance and pulse spectrum is b etter for p -p olarization. In the presence of TPP temp oral p rofiles of ultrashort pulses distor t. One can see tails on the trailing edges in cross-correlation functions. Tail of p-polarized pulse was approximated with function y = y0 + exp (-x/), where corresponds to the lifetime of TPP, which was found to b e 30 fs.


Fi g.1. ( col or onli ne) ( a) Dot s ­ cr oss-cor Inset ­ spectrum of r eflected pul se. (b) Cr cir cl es) pol ari zati on of i nci dent li ght. Bl ue refl ect ed pul se s for

relati on functi on of a pul se r efl ect ed fr om a 30 nm-thi ck gol d fi l m. Red ( sol id) cur ve ­ Gaussian fit . oss-corr elati on functi on of a pul se refl ect ed from t he Au/ PC sa mpl e for p- ( bl ack squar es) and s- (r ed (soli d) curve ­ Gaussi an fit. Gr een soli d l i ne ­ exponent i al appr oxi mation of the t ai l. I nset ­ spectr a of p- (bl ack cur ve) and s- (r ed cur ve) pol ari zati on. The pl ot s ar e se mi logarit hmi c.

4 . Conclusions It is shown that temp oral p rofile of femtosecond laser pulses reflected fr om A u/PC system modifies in the p resence of Tamm p lasmon-p olariton. Lifetime of TPP was estimated at 30 ± 1 fs fr om fitting the tail of cr oss-correlation function of p-polarized pulse with exponential function. 5 . References
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